As the conventional fluidized bed granulators, there are known those shown in FIGS. 6 and 7.
Shown in FIG. 6 is a continuous type fluidized bed granulator, wherein a powder material A is fed into the housing 1 of the bed granulator by a powder feeder 6 and forms a fluidized bed 2 by the help of the hot air B blown into the housing 1 from the bottom of the housing 1. Into the fluidized bed 2 is sprayed a binder fluid C together with compressed air D from a nozzle 3, whereby granules as a granulation product is produced. The granules are taken out via a powder discharging device 11. An agitator 4 are provided in the fluidized bed 2, whereby the fluidized state of the fluidized bed 2 is maintained well. A pulse air type bag filter 5 is provided at the top of the housing 1, whereby powder-gas separation is effected and the separated gas is discharged.
FIG. 7 is a batchwise fluidized granulator. The difference of this granulator from that of FIG. 6 is that this granulator, being batchwise, has no powder feeder 6, no powder discharging device 11 and, in the fluidized bed 2, no agitator 4 but has a bag filter 5 with a shaking device 7 at the top of the housing 1.
In these conventional fluidized granulators, the housing is constituted by a steel plate made of stainless steel or the like, and a bag filter is provided at the top of the housing to prevent the scattering of fine powder.
In the above conventional fluidized granulators, the bag filter is ordinarily shaken in order to prevent its clogging. Since air feeding is temporarily stopped during the shaking, the powder in the fluidized bed comes to a stationary state, whereby the powder in the fluidized bed, when being a highly hygroscopic powder such as amino acid or the like, causes blocking in some cases.
In order to solve the above problem, a pulse air type bag filter is used in some cases. However, since a large number of bags are arranged at small intervals, there occurs deposition of powder between the bags, resulting in the clogging of the bags.